Display devices such as liquid crystal display devices have rapidly spread in recent years and are used not only for televisions but also for a wide variety of devices such as electronic book readers, digital photo frames, industrial appliances, personal computers (PCs), tablet PCs, and smartphones. These devices are required to have various properties for the respective uses, and various liquid crystal display modes are developed.
Examples of the liquid crystal display modes include modes in which liquid crystal molecules are aligned in a direction substantially parallel to the main surfaces of the substrates when no voltage is applied (hereinafter, also referred to as horizontal alignment modes) such as the in-plane switching (IPS) mode and the fringe field switching (FFS) mode. Examples of the liquid crystal display modes also include modes in which liquid crystal molecules are aligned in a direction substantially perpendicular to the main surfaces of the substrates when no voltage is applied (hereinafter, also referred to as vertical alignment modes) such as the vertical alignment (VA) mode. In order to achieve such alignment control of liquid crystal molecules, use of an alignment film is proposed.
Patent Literature 1, for example, discloses the introduction of a specific silsesquioxane (SSQ) low-molecular-weight additive into a varnish for forming a liquid crystal alignment film containing a solvent and a polymer component including a polyamic acid, a soluble polyimide, a polyamide, a polyamideimide, or a mixture of two or more thereof, so as to increase the rubbing resistance and storage stability of the varnish
Patent Literature 2, for example, discloses the introduction of a specific silsesquioxane (SSQ) crosslinking agent into an alignment film including a polyamic acid and a polyimide so as to crosslink the polyamic acid and polyimide to increase the storage stability and rubbing resistance of the alignment film.